Having "discovered" the Arduino platform, I too looked around for a good starting point to immerse my 12-year old daughter into the world of electronics and robotics. Having grown up building many Heathkit projects I yearned to find a similar product. I found this in Parallax Inc.

Parallax has a number of successful products on the market. They sell what is referred to as a Robitcs Shield Kit for Arduino:

http://www.parallax.com/product/130-35000

This product was built upon their successful Boe-Bot concept; a robot chassis based upon the BASIC Stamp microcontroller that has been very popular in educational settings and with hobbyists. Parallax Inc. provides a complete set of documentation available as a free, online set of tutorials at:

http://learn.parallax.com/ShieldRobot

These lessons are reminiscent of the Heathkit style of teaching the theory while having fun building a kit.

Parallax built the Shield-Bot using their "Board of Education" concept which essentially provides a prototyping platform for the Arduino on top of the Robot chassis allowing an infinite number of sensors and communications devices to be integrated into the mobile platform. The tutorials leverage this BOE platform extensively to constructively "build-up" one's knowledge as each new electronic device is introduced and incorporated into the robot.

In addition to the basic Shield-Bot kit there are options including a gripper, wheel encoders, line followers, tank-track, sonar and infrared sensor options to extend the capabilities of the robot. It is a rich set of features and functions packed into a small yet capable product.

I highly recommend this kit to those looking for an inexpensive start into Arduino based robotics ($159 including an Arduino, $129 if you already own the Arduino).

@willb6: I like the look of the two-wheeled Turtle from DFRobot, along with their 2A dual motor controller.

Thanks for the feedback, but I've sort of gone a different way -- I found an interesting base with three wheels (those strange wheels that have sub wheels on the main wheels) -- then I found a motor controller from AdaFruit that control four motors -- I'll be writing all of this up in a future blog.

@Max: If you are ready to build your own robot from the ground up, let me offer my own approach.

I'm a LEGO fan since I was little child, and when I need to prototype something similar to a robot, I use to attach some bricks to the MCU boards until I get a nice Frankenstein-like thingy.

The last time I used LEGO plus electronics, I was trying to build a helicopter form factor drone: I bought a simple and big RC helicopter, a wifi enabled webcam and some LEGO Technics boxes to update my collection -- of course, the helicopter was destroyed in the first test flight ;-)

NOTE: In addition to LEGO Technics, now there are available kits for robotics such Mindstorm and NXT.

I like the look of the two-wheeled Turtle from DFRobot, along with their 2A dual motor controller.

The MAKE Rovera, which got one negative review, is actually a bigger, more expensive kit that appears to include the Turtle along with some other stuff, so I wouldn't let that one negative review cloud the DFRobot offering.